Solid oxide fuel cell stack

ABSTRACT

A fuel cell stack comprises a plurality of modules and each module comprises an elongate hollow member and one passage extending through the hollow member for the flow of a reactant. Each hollow member has a first flat surface and a second flat surface. At least one of the modules includes a plurality of fuel cells arranged on at least one of the first and second flat surfaces. Each module has a first and second integral feature to provide a spacer and a connection with its adjacent modules. The first integral feature comprises a third flat surface and the second integral feature comprises a fourth flat surface. The third flat surface is arranged at an intersecting angle to the first flat surface and the fourth flat surface is arranged at an intersecting angle to the second flat surface.

FIELD OF THE INVENTION

The present invention relates to a module for a fuel cell stack and inparticular to a module for a solid oxide fuel cell stack.

BACKGROUND OF THE INVENTION

It is known from published International patent application WO03010847A2to provide a plurality of modules for a fuel cell stack in which eachmodule comprises a hollow member. Each hollow member has at least onepassage extending longitudinally through the hollow member for the flowof a reactant. Each hollow member has two parallel flat surfaces and atleast one of the modules has a plurality of fuel cells arranged on theflat surfaces of the modules. The end of one module is connected to anend of an adjacent module to allow reactant to flow sequentially throughthe modules.

In WO03010847A2 spacer members are provided at the ends of the adjacentmodules to provide a connection for the flow of reactant from one moduleto the next, without leaks, and to space apart the flat surfaces of themodules. The spacer members are generally T-shaped or W-shaped incross-section.

A problem with this arrangement is that additional spacer members arerequired to fluidly connect and space apart the adjacent modules.

SUMMARY OF THE INVENTION

Accordingly the present invention seeks to provide a novel module for afuel cell stack, which reduces, and preferably overcomes, theabove-mentioned problem.

Accordingly the present invention provides a module for a fuel cellstack, the module comprises an elongate hollow member, the module has atleast one passage extending longitudinally through the hollow member forthe flow of a reactant, the hollow member has a first flat surface and asecond flat surface arranged substantially parallel to the first flatsurface and at least one end of the module has a first integral featureto provide a spacer with an adjacent module, the first integral featurecomprises a third flat surface arranged such that it is non coplanarwith the first flat surface.

Preferably the first integral feature provides a connection with theadjacent module.

Preferably a second end of the module has a second integral feature toprovide a spacer with another adjacent module, the second integralfeature comprises a fourth flat surface arranged such that it is noncoplanar with the second flat surface.

Preferably the second integral feature provides a connection with theother adjacent module.

Preferably the fourth flat surface is arranged parallel to the thirdflat surface.

Preferably the third flat surface is arranged at an intersecting angleto the first flat surface and the fourth flat surface is arranged at anintersecting angle to the second flat surface.

Preferably the first end decreases in thickness between the second flatsurface and the third flat surface.

Preferably the first end decreases in thickness between the second flatsurface and the third flat surface and the second end decreases inthickness between the first flat surface and the fourth flat surface.

Alternatively the second end increases in thickness between the firstflat surface and the fourth flat surface.

Preferably the intersecting angle is between 5° and 20°, more preferablythe intersecting angle is between 10° and 15°.

Alternatively the third flat surface is arranged parallel to the firstflat surface and the fourth flat surface is arranged parallel to thesecond flat surface.

Preferably a plurality of fuel cells are arranged on the first andsecond flat surfaces.

Preferably the fuel cells are solid oxide fuel cells.

Alternatively a reforming catalyst may be provided in the at least onepassage or on the first and second flat surfaces.

The present invention also provides a fuel cell stack comprises aplurality of modules, each module comprises an elongate hollow member,each module has at least one passage extending longitudinally throughthe hollow member for the flow of a reactant, each hollow member has afirst flat surface and a second flat surface arranged substantiallyparallel to the first flat surface, at least one of the modules includesa plurality of fuel cells, the fuel cells are arranged on at least oneof the first and second flat surfaces of the at least one module and atleast one end of at least one of the modules has a first integralfeature to provide a spacer with an adjacent module, the first integralfeature comprises a third flat surface arranged such that it is noncoplanar with the first flat surface.

Preferably at least one end of each of the modules has a first integralfeature to provide a spacer with an adjacent module, the first integralfeature comprises a third flat surface arranged such that it is noncoplanar with the first flat surface.

Preferably the first integral feature provides a connection with theadjacent module.

Preferably a second end of the at least one module has a second integralfeature to provide a spacer with another adjacent module, the secondintegral feature comprises a fourth flat surface arranged such that itis non coplanar with the second flat surface.

Preferably a second end of each module has a second integral feature toprovide a spacer with another adjacent module, the second integralfeature comprises a fourth flat surface arranged such that it is noncoplanar with the second flat surface.

Preferably the second integral feature provides a connection with theother adjacent module.

Preferably the fourth flat surface is arranged parallel to the thirdflat surface.

Preferably the third flat surface is arranged at an intersecting angleto the first flat surface and the fourth flat surface is arranged at anintersecting angle to the second flat surface.

Preferably the first end decreases in thickness between the second flatsurface and the third flat surface.

Preferably the first end decreases in thickness between the second flatsurface and the third flat surface and the second end decreases inthickness between the first flat surface and the fourth flat surface.

Alternatively the second end increases in thickness between the firstflat surface and the fourth flat surface.

Preferably the intersecting angle is between 5° and 20°, more preferablythe intersecting angle is between 10° and 15°.

Alternatively the third flat surface is arranged parallel to the firstflat surface and the fourth flat surface is arranged parallel to thesecond flat surface.

Preferably adjacent modules are connected to allow reactant to flowsequentially through the modules.

Alternatively adjacent modules are connected to allow reactant to flowin parallel through the modules.

Preferably the fuel cells are solid oxide fuel cells.

At least one of the modules may have a reforming catalyst provided inthe at least one passage or on the first and second flat surfaces.

Alternatively all of the modules have fuel cells.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully described by way of examplewith reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a module for a fuel cell stack accordingto the present invention.

FIG. 2 is a longitudinal cross-sectional view through the module shownin FIG. 1.

FIG. 3 is an end view of a fuel cell stack comprising a plurality ofmodules shown in FIGS. 1 and 2.

FIG. 4 is a cross-sectional view through the module shown in FIGS. 1 and2 showing the fuel cells.

FIG. 5 is a part cross-section view showing the electricalinterconnectors between modules.

FIG. 6 is a perspective view of an alternative module for a fuel cellstack according to the present invention.

FIG. 7 is a longitudinal cross-sectional view through the module shownin FIG. 6.

FIG. 8 is an end view of a fuel cell stack comprising a plurality ofmodules shown in FIGS. 6 and 7.

FIG. 9 is a longitudinal cross-sectional view through an alternativemodule according to the present invention.

FIG. 10 is a longitudinal cross-sectional view through an alternativemodule according to the present invention.

FIG. 11 is a longitudinal cross-sectional view through an alternativemodule according to the present invention.

FIG. 12 is a longitudinal cross-sectional view through an alternativemodule according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A solid oxide fuel cell stack 10 according to the present invention isshown in FIGS. 1 to 5. The solid oxide fuel cell stack 10 comprises aplurality of modules 12 arranged within a casing (not shown). Eachmodule 12 comprises an elongate hollow member 14. The hollow members 14are manufactured from fully or partially stabilised zirconia, alumina,silicon carbide, magnesia doped magnesia aluminate or other suitableceramic material. Each hollow member 14 has two flat parallel surfaces16 and 18 upon which, are arranged solid oxide fuel cells 20. The hollowmembers 14 are porous, or have apertures, to allow fuel to flow to thesolid oxide fuel cells 20.

The solid oxide fuel cells 20 are spaced apart longitudinally along thesurfaces 16 and 18 and the solid oxide fuel cells 20 on each of thesurfaces 16 and 18 are electrically connected in series.

Each solid oxide fuel cell 20 comprises an anode electrode 22, a solidoxide electrolyte 24 and a cathode electrode 26. The anode electrodes 22of all but one of the fuel cells 22, on each of the surfaces 16 and 18,are electrically connected to the cathode electrode 26 of an adjacentsolid oxide fuel cell 18 by a respective one of a plurality ofinterconnectors 28.

Each hollow member 14 has one or more passages 31 extendinglongitudinally through the hollow member 14, for the supply of fuel tothe solid oxide fuel cells 20. The fuel diffuses, or flows, through thehollow members 14 to the anode electrodes 22 of the solid oxide fuelcells 20. The passages 31 in each hollow member 14 have a uniformcross-sectional area throughout its length.

A first end 30 and a first side 32 of the module 12 has a first feature34 to provide a spacer and a fluid connection with an adjacent module 12and a second end 38 and a second side 40 of the module 12 has a secondfeature 42 to provide a spacer and a fluid connection with anotheradjacent module 12. The first feature 34 comprises a third flat surface36 and the second feature 42 comprises a fourth flat surface 44 arrangedparallel to the third flat surface 36. The third flat surface 36 isarranged at an intersecting angle θ to the first flat surface 16 and thefourth flat surface 44 is arranged at an intersecting angle θ to thesecond flat surface 18. The intersecting angle θ is between 5° and 20°.Preferably the intersecting angle θ is between 10° and 15°. The thirdflat surface 36 of one module 12 is arranged to abut the fourth flatsurface 44 of an adjacent module 12. The third flat surface 36 of onemodule 12 has one or more apertures 48 arranged to align withcorresponding apertures 50 in the fourth flat surface 44 of the adjacentmodule 12. The third flat surface 36 of one module 12 has an electricalinterconnector 52 to electrically connect an electrical interconnector54 at the fourth flat surface 44 of the adjacent module 12 toelectrically connect the solid oxide fuel cells 20 in electrical series.

Thus each module 12 is arranged such that the surfaces 16 and 18 of thehollow member 14 are substantially parallel and spaced apart. Themodules 12 are arranged such that the surfaces 16 and 18 of adjacentmodules 12 are spaced apart. Additionally, it is to be noted that themodules 12 are arranged to form an undulating arrangement of modules 12.Thus it is clear that the fuel flows sequentially through the modules 12from a fuel supply manifold to a fuel removal manifold through aserpentine flow path as shown in FIG. 3.

Additionally air, or oxygen, flows through the space between the modules12 in a direction perpendicular to the longitudinal direction of themodules 12.

The hollow members may be produced by extruding, injection moulding,near net shape techniques, casting or forging. The hollow members mayalso comprise metals or polymers.

The advantage of the present invention is that there is a reduction inthe number of parts of the fuel cell stack, because the separate spacermembers are dispensed with. There is a reduction of interfaces withinthe fuel cell stack. There is a high packing density of the fuel cells.The ability to withstand thermal gradients and thermal cycling ismaintained.

An alternative fuel cell stack 10B is shown in FIGS. 6 to 8 and likeparts are denoted by like numerals. Again the first end 30 and a firstside 32 of the module 12B has a first feature 34 to provide a spacer anda fluid connection with an adjacent module 12 and a second end 38 and asecond side 40 of the module 12 has a second feature 42 to provide aspacer and a fluid connection with another adjacent module 12. The firstfeature 34 comprises a third flat surface 36 and the second feature 42comprises a fourth flat surface 44 arranged parallel to the third flatsurface 36. The embodiment in FIG. 6 to 8 differs in that the third flatsurface 36 is arranged parallel to the first flat surface 16 and thefourth flat surface 44 is arranged parallel to the second flat surface18.

In this arrangement the reactant may flow sequentially through themodules or in parallel through the modules from inlet and outletmanifolds at the ends of the modules.

This arrangement also has advantages of maintaining a gap between themodules with an inlet manifold and an outlet manifold. Also providesimproved durability. This arrangement also provides constant gap betweenthe modules, which is advantageous for the flow of one of the reactants,the air, between the modules.

A further possibility of module 12C, as shown in FIG. 9, is to providean arrangement similar to FIGS. 1 to 5 where the first feature 34comprises a third flat surface 36 and the second feature 42 comprises afourth flat surface 44 but the fourth flat surface 44 is not arrangedparallel to the third flat surface 36. The third flat surface 36 isarranged at an intersecting angle θ to the first flat surface 16 and thefourth flat surface 44 is arranged at an intersecting angle θ to thesecond flat surface 18. The intersecting angle θ is between 5° and 20°.Preferably the intersecting angle θ is between 10° and 15°. In FIGS. 1to 5 both of the first and second ends 30 and 38 decrease in thicknessbetween the first and second sides 32 and 40, that is the distance, orthickness, between the third surface 36 and the second surface 18decreases to produce a decrease in thickness to the first end 30 of themodule 12 and likewise the distance, or thickness, between the fourthsurface 44 and the first surface 16 decreases such as to produce adecrease in thickness to the second end 38 of the module 12. In thisembodiment the first end 30 decreases in thickness between the thirdsurface 36 and the second surface 18 and the second end 38 increases inthickness between the fourth surface 44 and the first surface 16. Thearrangement may be arranged to provide a constant gap between themodules 12

Another possibility of module 12D, as shown in FIG. 10, is similar tothat shown in FIG. 7 but the fourth flat surface 44 is coplanar with thesecond flat surface 18.

Another possibility of module 12E, as shown in FIG. 11, is similar tothat shown in FIG. 2 but the fourth flat surface 44 is coplanar with thesecond flat surface 18.

A further possibility of module 12F, as shown in FIG. 12, is similar tothat shown in FIG. 7 but the there is a ramp between the fourth flatsurface 44 and the second flat surface 18 and a ramp between the thirdflat surface 36 and the first flat surface 16.

It is also possible to use the modules in FIG. 2 or 7 with modules inwhich both of the ends are coplanar with the first and second surfaces.

Thus the present invention uses at least one flat surface, which is notcoplanar with the major flat surface of the module and either the flatsurface intersects the major flat surface of the module or the flatsurface is parallel to and is spaced, upstanding, from the major flatsurface of the module.

Although the present invention has been described with reference tosolid oxide fuel cells, the present invention is equally applicable toother types of fuel cells.

Although the present invention has been described with reference tosolid oxide fuel cells being provided on all of the modules, it may bepossible for at least one of the modules to have a reforming catalystprovided in the at least one passage or on the first and second flatsurfaces rather than being provided with fuel cells.

Although the present invention has been described with reference to themodules being connected in serial flow relationship for the flow offluid, it may be possible for them to be connected in parallel flow.

1. A fuel cell stack comprising: a plurality of modules, each modulecomprises an elongate hollow member, each module has at least onepassage extending longitudinally through the hollow member for the flowof a reactant, each hollow member has a first flat surface and a secondflat surface arranged substantially parallel to the first flat surface,a first one of the modules includes a plurality of fuel cells, the fuelcells are arranged on at least one of the first and second flat surfacesof the first one of the modules, a first end of the first one of themodules has a first integral spacer formed integrally with said moduleto provide space from a second one of the modules, the first integralspacer comprises a third flat surface arranged such that it is noncoplanar with the first flat surface of the first one of the modules, asecond end of the second one of the modules has a second integral spacerformed integrally with the second one of the modules to provide a spacerwith the first one of the modules, the second integral spacer comprisesa fourth flat surface arranged such that it is non coplanar with thesecond flat surface of the second one of the modules, the third flatsurface of the first one of the modules is arranged to abut the fourthflat surface of the second one of the modules, the third flat surfacehas at least one aperture for the flow of reactant, the fourth flatsurface has at least one aperture for the flow of reactant and the atleast one aperture in the third flat surface is aligned with the atleast one aperture in the fourth flat surface to provide a fluidconnection between the first and second ones of the modules withoutadditional separate spacers between the first and second ones of themodules.
 2. A fuel cell stack as claimed in claim 1, wherein a first endof each module has a first integral spacer formed integrally with saidmodule, a second end of each module has a second integral spacer formedintegrally with said module, each first integral spacer comprises athird flat surface arranged such that it is non coplanar with the firstsurface of said module and each second integral spacer comprises afourth flat surface arranged such that it is non coplanar with thesecond surface of said module.
 3. A fuel cell stack as claimed in claim1 wherein the fourth flat surface is arranged parallel to the third flatsurface.
 4. A fuel cell stack as claimed in claim 1 wherein the thirdflat surface is arranged at a first intersecting angle to the first flatsurface and the fourth flat surface is arranged at a second intersectingangle to the second flat surface.
 5. A fuel cell stack as claimed inclaim 4 wherein the first end decreases in thickness between the secondflat surface and the third flat surface.
 6. A fuel cell stack as claimedin claim 5 wherein the first end decreases in thickness between thesecond flat surface and the third flat surface and the second enddecreases in thickness between the first flat surface and the fourthflat surface.
 7. A fuel cell stack as claimed in claim 5 wherein thesecond end increases in thickness between the first flat surface and thefourth flat surface.
 8. A fuel cell stack as claimed in claim 4 whereinthe first and second intersecting angles are between 5° and 20°.
 9. Afuel cell stack as claimed in claim 4 wherein the first and secondintersecting angles are between 10° and 15°.
 10. A fuel cell stack asclaimed in claim 1 wherein the third flat surface is arranged parallelto the first flat surface and the fourth flat surface is arrangedparallel to the second flat surface.
 11. A fuel cell stack as claimed inclaim 1 wherein adjacent modules are connected to allow reactant to flowsequentially through the modules.
 12. A fuel cell stack as claimed inclaim 1 wherein adjacent modules are connected to allow reactant to flowin parallel through the modules.
 13. A fuel cell stack as claimed inclaim 1 wherein the fuel cells are solid oxide fuel cells.
 14. A fuelcell stack as claimed in claim 1 wherein at least one of the modules hasa reforming catalyst provided in the at least one passage or on thefirst and second flat surfaces.
 15. A fuel cell stack as claimed inclaim 1 wherein all of the modules have fuel cells.
 16. A fuel cellstack as claimed in claim 1 wherein a second end of a further module hasa second integral spacer to provide a spacer with the at least onemodule, the second integral spacer comprises a fourth flat surfacearranged such that it is non coplanar with the second flat surface ofthe further module, the third flat surface of the at least one moduleabuts the fourth flat surface of the further module.